Breather device and engine

ABSTRACT

This breather device separates engine oil included in a blow-by gas. The breather device comprises a first route, an acceleration route, a branching route, and turn-back routes. The blow-by gas flows to the first route. The acceleration route is connected to a downstream side of the first route, and has a flow channel cross-sectional area smaller than that of the first route. The branching route is connected to a downstream side of the acceleration route, configured including a wall part orthogonal to the acceleration route, and branched into two routes by the wall part. The turn-back routes are connected to one route branching at the branching route, and are turned back so as to be parallel to the acceleration route and to head in the opposite direction from a progressing direction.

CROSS-REFERENCE

This application is a US National Stage Application under 35 U.S.C. §371 of International Application No. PCT/JP2019/018374 filed May 8,2019, which claims foreign priority of JP2018-105726 filed May 31, 2018,the disclosures of which are hereby incorporated by reference in theirentirety.

TECHNICAL FIELD

The present invention mainly relates to a breather device that separatesengine oil contained in blow-by gas.

BACKGROUND ART

In Patent Literature 1, a cylinder head cover having a function ofseparating engine oil contained in blow-by gas that has leaked from acombustion chamber is disclosed. This head cover is formed with a gaschannel through which the blow-by gas introduced from a cylinder headside is discharged to the outside. This gas channel is formed with ahigh-pressure portion having a small channel cross-sectional area. Theblow-by gas, a speed of which is accelerated to a high speed whenflowing through the high-pressure portion, collides with a wall portion.In this way, the engine oil contained in the blow-by gas is separated.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Unexamined Patent Application    Publication No. 2017-150435

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, the engine oil contained in the blow-by gas is not sufficientlyseparated in the configuration disclosed in Patent Literature 1, andthus improvement of the configuration has been desired.

The present invention has been made in view of the above circumstance,and a main object thereof is to provide a breather device having aconfiguration capable of sufficiently separating engine oil contained inblow-by gas.

Means for Solving the Problems

The problem to be solved by the present invention is as described above.Next, a description will be made on means for solving the problem andeffects thereof.

A first aspect of the present invention provides a breather devicehaving the following configuration. That is, this breather deviceseparates engine oil contained in blow-by gas. This breather deviceincludes a first route, an acceleration route, a branching route, and aturn-back route. The blow-by gas flows through the first route. Theacceleration route is connected to a downstream side of the first routeand has a smaller channel cross-sectional area than the first route. Thebranching route is connected to a downstream side of the accelerationroute, includes a wall portion that is orthogonal to the accelerationroute, and is branched into two routes by the wall portion. Theturn-back route is connected to one of the branched routes of thebranching route and is turned back in a manner to be parallel to theacceleration route and to have a reverse advancing direction from thatof the acceleration route.

In this way, the engine oil mist contained in the blow-by gas is carriedby the blow-by gas, a flow rate of which is increased in theacceleration route, and collides with the wall portion in the branchingroute. As a result, the engine oil can be separated from the blow-bygas. In addition, since the turn-back route causes the blow-by gas toturn back, the engine oil can be separated from the blow-by gas byinertia.

The breather device includes a portion in which an advancing directionof the route is changed by 90 degrees. Outer wall portions constitutingsuch a portion are constructed of two wall portions that are orthogonalto each other and are connected to each other.

In this way, compared to the case where the wall portions constitutingan outer side of a corner portion are connected by an arcuate surface, aflow of the blow-by gas is likely to be disturbed and stagnate, and aflow rate of the blow-by gas is likely to be reduced. In particular, theengine oil mist having a small particle diameter is likely to becollected in a location, where the stagnation occurs, on the outer sideof the corner portion. As a result, it is possible to further reliablyseparate the engine oil from the blow-by gas.

The breather device preferably includes a merging route that is formedon a downstream side of the branching route and that merges the twobranched routes of the branching route.

As a result, the engine oil that is contained in the two branched routescan collide with each other. Thus, it is possible to further reliablyseparate the engine oil from the blow-by gas.

The breather device preferably has the following configuration. That is,this breather device includes a receiving portion that receives theengine oil separated from the blow-by gas. The receiving portionincludes an oil delivery portion that delivers the engine oil separatedfrom the blow-by gas. The oil delivery portion is a stepped grooveportion in which an up portion and a down portion are alternately andrepeatedly provided. A height of the up portion is increased toward adownstream side of a route through which the engine oil returns. Aheight of the down portion is reduced toward the downstream side of theroute through which the engine oil returns. The height of the downportion is changed more steeply than that of the up portion.

In this way, the engine oil can move along the up portion by vibrationof the engine. Meanwhile, since the height of the down portion issteeply changed, the engine oil is less likely to flow reversely. As aresult, it is possible to further reliably move the engine oil.

A second aspect of the present invention provides an engine having thefollowing configuration. That is, this engine includes the breatherdevice and a vaporizer. The vaporizer vaporizes liquid fuel by usingheat of an engine coolant. The breather device is cooled when the enginecoolant that has been subjected to heat exchange with the vaporizerflows through the breather device.

It is possible to increase viscosity of the engine oil by cooling theblow-by gas in the breather device using the engine coolant, atemperature of which has been reduced by the heat exchange with thevaporizer. Thus, it is possible to further reliably separate the engineoil from the blow-by gas.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating flows of intake air/exhaust gas,a coolant, fuel gas, and the like, of an engine according to anembodiment of the present invention.

FIG. 2 is a schematic view illustrating a configuration of the engine.

FIG. 3 is a bottom view illustrating an oil separation route formed in aceiling portion.

FIG. 4 is an enlarged view of a fourth region of the oil separationroute.

FIG. 5 is a plan view illustrating an oil return hole and an oildelivery portion that are formed in a receiving portion.

FIG. 6 is a cross-sectional view illustrating an up portion and a downportion of the oil delivery portion.

DESCRIPTION OF EMBODIMENTS

Next, a description will be made on an embodiment of the presentinvention with reference to the drawings. FIG. 1 is a schematic viewillustrating flows of intake air/exhaust gas, fuel gas, and the like ofan engine 100 according to the embodiment of the present invention. FIG.2 is a schematic view of the engine 100.

The engine 100 illustrated in FIG. 1 is a gas engine that generatespower by burning the fuel gas such as petroleum gas or natural gas. Theengine 100 may be another type of the internal combustion engine such asa gasoline engine or a diesel engine. The engine 100 is used as a drivesource of a generator, a heat pump, a mobile body, or the like, forexample. As illustrated in FIG. 1 and the like, this engine 100includes, as main components, an intake section 1, an exhaust section 2,and a fuel gas supply section 3, a cooling section 4, an engine body 5,and a blow-by gas recirculation section 6, for example.

The intake section 1 suctions air from the outside. The intake section 1includes an intake pipe 11, an air cleaner 12, a throttle valve 13, andan intake manifold 14.

The intake pipe 11 constitutes an intake route, and the air that hassuctioned from the outside (hereinafter, intake air) can flow toward theengine body 5 through the intake pipe 11.

The air cleaner 12 includes a cleaner element for removing foreignsubstances in the intake air. The intake air that has been purified whenflowing through the air cleaner 12 is delivered to the intake manifold14.

The throttle valve 13 is arranged in an intermediate portion of theintake route. An opening degree of the throttle valve 13 is changedaccording to a control command from an engine control unit (ECU), whichis not illustrated. In this way, the throttle valve 13 changes a channelcross-sectional area. As a result, it is possible to adjust an amount ofthe intake air to be supplied to the intake manifold 14 via the throttlevalve 13.

The intake manifold 14 is connected to a downstream end portion of theintake pipe 11 in a flow direction of the intake air. The intakemanifold 14 divides the intake air, which has been supplied via theintake pipe 11, according to the number of cylinders 50 and can therebysupply the intake air to a combustion chamber in each of the cylinders50.

Each of the cylinders 50 is formed with a combustion chamber 50 a. Thegaseous fuel gas that is supplied from the fuel gas supply section 3 isdistributed and introduced into the combustion chamber 50 a of each ofthe cylinders 50. A detailed description on a configuration of the fuelgas supply section 3 will be made below.

In the combustion chamber 50 a, mixed gas in which the gaseous fuel gasand the intake air supplied from the intake manifold 14 are mixed iscompressed and ignited at appropriate timing by an appropriate method(for example, ignition by a spark plug). A piston, which is notillustrated and is arranged in the cylinder 50, reciprocates linearly bya propulsive force that is obtained by explosion in the combustionchamber 50 a. The thus-obtained power is converted into circular motionvia a crankshaft, which is not illustrated, and the like and istransmitted to an appropriate device.

The exhaust section 2 discharges the exhaust gas that is produced in thecombustion chamber 50 a to the outside. As illustrated in FIG. 1 , theexhaust section 2 includes an exhaust pipe 21, an exhaust manifold 22,and an exhaust gas purifier 23.

The exhaust pipe 21 constitutes an exhaust route, and the exhaust gasthat has been produced in the combustion chamber 50 a can flowtherethrough to the outside.

The exhaust manifold 22 is connected to an upstream end portion of theexhaust pipe 21 in a flow direction of the exhaust gas. The exhaustmanifold 22 collectively guides the exhaust gas produced in thecombustion chambers 50 a to the exhaust pipe 21.

The exhaust gas purifier 23 is provided in a downstream end portion ofthe exhaust pipe 21. The exhaust gas purifier 23 uses a catalyst or thelike to remove harmful components and particulate matters such asnitrogen oxide (NOx), carbon monoxide (CO), and hydrocarbons (HC)contained in the exhaust gas, and thereby purifies the exhaust gas.

As illustrated in FIG. 1 , the fuel gas supply section 3 includes a fuelgas supply pipe 31, a fuel gas tank 32, a vaporizer 33, and a fuel gasvalve 34.

The fuel gas supply pipe 31 constitutes a fuel gas supply route throughwhich the fuel gas is supplied from the fuel gas tank 32 to thecombustion chamber 50 a. In an intermediate portion of this fuel gassupply route, the fuel gas valve 34 and the vaporizer 33 are arranged inthis order from an upstream side in a flow direction of the fuel gas.

The fuel gas tank 32 stores liquid fuel gas such as LPG. The fuel gastank 32 is connected to an upstream end portion of the fuel gas supplypipe 31 in the flow direction of the fuel gas. The liquid fuel gas thatis stored in the fuel gas tank 32 is supplied to the vaporizer 33 by apressure, a fuel pump, which is not illustrated, or the like.

The vaporizer 33 is a water-heated vaporizer, and vaporizes the liquidfuel gas supplied from the fuel gas tank 32. More specifically, theliquid fuel gas that is supplied to the vaporizer 33 is depressurized,and heat of the liquid fuel gas is exchanged with a heat medium such asa coolant (an engine coolant) for cooling the engine 100. In this way,the fuel gas can be vaporized. The vaporizer 33 may be configured tovaporize the liquid fuel gas without using the coolant. In addition, inthe case where the engine 100 is the gasoline engine or the dieselengine, the fuel does not have to be vaporized. Thus, the vaporizer 33is unnecessary.

The engine body 5 is a component that burns the fuel to generate thepower. As illustrated in FIG. 2 , the engine body 5 includes an oil pan51, a cylinder block 52, a cylinder head 53, a head cover 54, and a gearcase 55.

The oil pan 51 is a container for storing the engine oil that islubricating oil for the engine 100. The oil pan 51 is provided in alower portion of the engine 100. The oil pan 51 is formed as thecontainer, an upper portion of which is opened, and an internal storagespace and the cylinder block 52 communicate with each other. In thisway, the engine oil that has flowed through the cylinder block 52 caneasily return to the oil pan 51.

The engine oil that is stored in the oil pan 51 is suctioned by anengine oil pump, which is not illustrated and is provided to the engine100, and is thereafter supplied to each of the sections (for example,inside of the cylinder block 52 and inside of the gear case 55) of theengine 100. The engine oil that has flowed through the sections of theengine 100 returns to the oil pan 51 and is stored therein.

The cylinder block 52 is attached to an upper side of the oil pan 51.The cylinder block 52 is formed with a space for accommodating thecrankshaft and the like and the plural cylinders 50 in each of which thepiston is accommodated.

The cylinder head 53 is attached to an upper side of the cylinder block52. Together with the cylinder block 52, the cylinder head 53constitutes the above-described combustion chamber 50 a. An injector forinjecting the fuel is attached to the cylinder head 53.

The head cover 54 is provided on an upper side of the cylinder head 53,and accommodates a valve operation mechanism including a push rod, arocker arm, and the like, which are not illustrated and operate anintake valve and an exhaust valve.

The gear case 55 is arranged on a side surface of the cylinder block 52,the cylinder head 53, or the like (in detail, a side surface at an endin a direction of the crankshaft). In the gear case 55, a crank gear, avalve operation gear, a pump gear, and the like are arranged. When thecrank gear rotates according to rotation of the crankshaft, the valveoperation gear and the pump gear, each of which meshes with the crankgear, rotate. In this way, the valve operation mechanism and the engineoil pump are operated in synchronization with the rotation of thecrankshaft.

The blow-by gas recirculation section 6 collects the blow-by gas that isproduced in the engine body 5, and returns the blow-by gas to the intakeroute. More specifically, the blow-by gas leaks from the combustionchamber 50 a into the cylinder block 52, and flows to the cylinder head53 and the head cover 54. The above flow of the blow-by gas from thecylinder block 52 to the head cover 54 is an example, and the flow ofthe blow-by gas differs by a configuration of the engine body 5, and thelike. As illustrated in FIG. 1 and FIG. 2 , the blow-by gasrecirculation section 6 includes a breather device 61, a blow-by gasrecirculation pipe 62, and a PCV valve 63.

The breather device 61 is arranged on top of the head cover 54. Thebreather device 61 is integrally formed with the head cover 54, andreleases the blow-by gas to maintain a balance between an internalpressure of the cylinder block 52 and atmospheric pressure. The breatherdevice 61 may be a different component from the head cover 54. An oilseparation route is formed between a ceiling portion 61 a that is alower surface of an upper plate (a lid portion) of the breather device61 and a plate-shaped receiving portion 61 b that is arranged below theceiling portion 61 a. The engine oil mist that is contained in theblow-by gas is separated when flowing through the oil separation route,drops to the receiving portion 61 b, and returns into the cylinder block52. A detailed description on this oil separation route will be madebelow.

The blow-by gas recirculation pipe 62 constitutes a route through whichthe blow-by gas discharged from the breather device 61 is delivered tothe intake manifold 14. The blow-by gas recirculation pipe 62 may beconfigured to connect the breather device 61 and the intake pipe 11(particularly, a portion on a downstream side of the throttle valve 13and on an upstream side of the intake manifold 14 in the flow directionof the intake air).

The PCV valve 63 is arranged between the breather device 61 and theblow-by gas recirculation pipe 62. PCV stands for positive crankcaseventilation. The PCV valve 63 is configured to be opened when the intakesection 1 has a negative pressure during operation of the engine 100,and the like to move the blow-by gas to the blow-by gas recirculationpipe 62.

The cooling section 4 circulates the coolant such as water to cool theengine 100. The engine body 5 is formed with a water jacket, which isnot illustrated, and the coolant, which has flowed through the waterjacket, and a temperature of which is increased, is cooled by a coolersuch as a radiator or a cooling tower. This coolant is also supplied tothe vaporizer 33 and the breather device 61. Hereinafter, a specificdescription will be made. As illustrated in FIG. 1 , the cooling section4 includes a first coolant pipe 41, a second coolant pipe 42, a thirdcoolant pipe 43, and a coolant pump 44.

The first coolant pipe 41 constitutes a route through which the coolantis supplied to the vaporizer 33. The coolant pump 44 pumps out thecoolant and thereby supplies the coolant to the vaporizer 33 via thefirst coolant pipe 41. In addition, a route, which is not illustrated,for heat exchange between the coolant and the vaporizer 33 is formed inthe vaporizer 33. A temperature of the coolant flowing through the firstcoolant pipe 41 is higher than a temperature of the vaporizer 33.Accordingly, due to the heat exchange between the coolant and thevaporizer 33, the temperature of the coolant is reduced, and thetemperature of the vaporizer 33 is increased. In this way, thevaporization of the fuel gas can be promoted.

The second coolant pipe 42 constitutes a route through which thecoolant, the temperature of which is reduced by the heat exchange withthe vaporizer 33, is supplied to the breather device 61. The route,which is not illustrated, for the heat exchange between the coolant andthe breather device 61 is formed in the breather device 61. In this way,the temperature of the coolant is increased, and a temperature of thebreather device 61 is reduced. When the temperature of the breatherdevice 61 is reduced, viscosity of the engine oil that is contained inthe blow-by gas flowing through the breather device 61 can be increased.As a result, particles of the engine oil mist can easily be bonded, andthus the engine oil can further reliably be separated. The coolant thathas been cooled by the cooler such as the radiator may be supplied tothe breather device 61.

The third coolant pipe 43 constitutes a route through which the coolant,the temperature of which is increased by the heat exchange with thebreather device 61, returns to the coolant pump 44.

Next, a description will be made on the oil separation route formed inthe breather device 61 with reference to FIG. 2 to FIG. 5 . In thefollowing description, terms for explaining directions such as paralleland orthogonal include configurations deviating from the parallel ororthogonal direction due to a manufacturing error or another reasoninstead of only strictly including configurations such as parallel andorthogonal. The same applies to terms related to not only the directionsbut also lengths. In FIG. 5 , a wall portion that is formed in theceiling portion 61 a is indicated by a chain line for reference.

As illustrated in FIG. 3 , the plural wall portions that are projecteddownward are formed in the ceiling portion 61 a of the breather device61 in this embodiment. The receiving portion 61 b includes a flatreceiving plate 91. When the wall portion that is projected from theceiling portion 61 a comes in contact with the receiving plate 91, aspace between the ceiling portion 61 a and the receiving portion 61 b ispartitioned by this wall portion, and the above oil separation route isformed by this configuration. The wall portion that constitutes the oilseparation route may be formed not on the ceiling portion 61 a side buton the receiving portion 61 b side.

As illustrated in FIG. 3 , the ceiling portion 61 a is formed with anintroduction portion 71. The introduction portion 71 is a portion thatis surrounded by the wall portion. In addition, as illustrated in FIG. 5, the receiving plate 91 of the receiving portion 61 b is formed with anoil return hole 92 at a position corresponding to the introductionportion 71. The blow-by gas that is produced in the engine body 5 flowsto the introduction portion 71 via the oil return hole 92. A guide plate72 as one of the wall portions for partitioning the introduction portion71 is formed with a clearance at an upper end (a deep side of the sheetin FIG. 3 ). The blow-by gas that has flowed to the introduction portion71 flows through the clearance at the upper end of the guide plate 72and then flows down. A catching net 73 is arranged in a route throughwhich this blow-by gas flows down. The catching net 73 is configured tobe able to catch the engine oil contained in the blow-by gas. The engineoil caught by the catching net 73 returns to the oil pan 51 via thecylinder block 52 and the cylinder head 53 through the oil return hole92.

The catching net 73 can catch only some of the engine oil. For example,the engine oil mist having a small particle diameter tends to passthrough the catching net 73. In the oil separation route, the engine oilmist contained in the blow-by gas, which has passed through the catchingnet 73, is separated and collected.

As illustrated in FIG. 3 , the oil separation route includes a firstregion 74, a second region 75, a third region 76, a fourth region 77,and a fifth region 78. In FIG. 3 , a flow direction of the blow-by gasis indicated by a bold arrow. The first region 74 is a region where theintroduction portion 71, the guide plate 72, and the catching net 73 arearranged. The blow-by gas that has been introduced in the breatherdevice 61 first flows through the first region 74. The second region 75to the fifth region 78 are arranged around the first region 74. Thesecond region 75 to the fifth region 78 are directly connected to thefirst region 74. As a result, the blow-by gas introduced from theintroduction portion 71 also flows to all the regions from the secondregion 75 to the fifth region 78. The second region 75 to the fifthregion 78 are mutually connected in an order of the region numbers. Theblow-by gas introduced from the introduction portion 71 finally flows tothe fifth region 78 regardless of the mediating route. A route, which isnot illustrated and is connected to the above-described PCV valve 63, isformed in the fifth region 78. Accordingly, the blow-by gas guided tothe fifth region 78 flows to the intake route via the PCV valve 63.

In each of the second region 75, the third region 76, and the fourthregion 77, a portion where the route is branched, a portion where thebranched routes are merged, a portion where a direction of the route ischanged (particularly, a portion where the direction of the route ischanged 180 degrees and reversed), and the like are formed. Theseparated engine oil drops to the receiving plate 91 of the receivingportion 61 b, and then finally returns to the oil pan 51 via the oilreturn hole 92.

A detailed description will hereinafter be made on the routes in thefourth region 77 and the separation of the engine oil from the blow-bygas. As illustrated in FIG. 4 , a first route 81, an acceleration route82, a branching route 83, a turn-back route 84, a reverse route 85, anda merging route 86 are formed in the fourth region 77.

In the route from the third region 76 to the fifth region 78 via thefourth region 77, the first route 81 is a route on the most upstreamside in the fourth region 77. Accordingly, the blow-by gas that hasflowed through the third region 76 is introduced into the first route81. In addition, the blow-by gas that has directly flowed from the firstregion 74 (without the second region 75 and the third region 76 beingintervened) is introduced into the first route 81.

The acceleration route 82 is a straight route that is connected to adownstream end of the first route 81. The acceleration route 82 has asmaller channel cross-sectional area than another route such as thefirst route 81. More specifically, a height in a vertical direction ofthe acceleration route 82 is lower than heights of the first route 81and the other routes. In other words, an upper surface of theacceleration route 82 is located lower than those of the other routes(located on a near side of the sheet from the other routes in FIG. 4 ).In this way, a flow rate of the blow-by gas can be increased by theacceleration route 82.

The acceleration route 82 may be configured to have the smaller channelcross-sectional area than the others by reducing an axial length to beshorter than those of the other routes. In addition, a shape of theacceleration route 82 is not limited to the straight-line shape, and theacceleration route 82 may include a curved portion.

The branching route 83 is connected to a downstream end of theacceleration route 82. The branching route 83 includes a wall portionthat is orthogonal to a direction of the acceleration route 82 (adirection along the route or an advancing direction, the same applieshereinafter). In the case where the acceleration route 82 is not thestraight route, a direction of a portion of the acceleration route 82that is connected to the branching route 83 (that is, a most downstreamroute) only needs to be orthogonal to the wall portion of the branchingroute 83. When the high-speed blow-by gas that has flowed along theacceleration route 82 collides with the wall portion of the branchingroute 83, the particles of the engine oil mist are separated. Asillustrated in FIG. 4 , in particular, the particles, each of which hasa large diameter and is easily affected by inertia, are easily separatedin this wall portion.

The branching route 83 includes a portion that is branched into tworoutes by this wall portion. These two routes are formed in a directionalong the wall portion, and thus are orthogonal to the accelerationroute 82. In addition, directions of these two routes differ from eachother by 180 degrees. When the branched portions are provided along withthe wall portion, just as described, the flow of the blow-by gas aroundthe wall portion can be complicated. In this way, it is possible tofurther reliably separate the engine oil from the blow-by gas.

The two routes that are branched in the branching route 83 may not beorthogonal to the acceleration route 82. That is, in order to cause theblow-by gas to collide with the wall portion (to prevent the flowthereof along the wall portion), the wall portion of the branching route83 has to be orthogonal to the acceleration route 82. However, thedirections of the two routes may be changed from this wall portion andmay thereby be separated. In addition, a difference in the directions ofthe two routes that are branched in the branching route 83 may be otherthan 180 degrees.

The turn-back route 84 is connected to a downstream end of the branchingroute 83. The two downstream ends of the branching route 83 are present,and the turn-back route 84 is formed at each of the two downstream ends.The turn-back route 84 may be connected to only one of the downstreamends of the branching route 83. The turn-back route 84 is a route thatis parallel to the acceleration route 82 and an advancing direction ofwhich is opposite from that of the acceleration route 82. The engine oilthat is not separated by the collision with the wall portion of thebranching route 83 tends to flow as is along the wall portion. Thus,when the direction of the route is significantly changed, the engine oilhaving the particularly large particle diameter is collected. In thisway, it is possible to further reliably separate the engine oil from theblow-by gas.

The reverse route 85 is connected to a downstream end of each of the twoturn-back routes 84. The reverse route 85 is a route, a direction ofwhich is changed such that an advancing direction thereof is changed by180 degrees. The reverse route 85 may be connected to one of thebranched routes by the branching route 83 via the turn-back route 84.

The reverse route 85 in this embodiment is not reversed in an arc shapebut is reversed by two right-angled routes. More specifically, thereverse route 85 is formed with, as an outer wall portion constitutingthe reverse route 85, a first wall portion 85 a, a second wall portion85 b, and a third wall portion 85 c. These three wall portions aredirectly connected to each other without an arcuate surface or the likebeing interposed. In other words, two routes, directions of which arechanged at right angle, are provided. Compared to the routes that areconnected to each other via the arcuate surface, in such routes, theflow of the blow-by gas stagnates or is disturbed, or the flow rate ofthe blow-by gas is reduced. In particular, the engine oil having thesmall particle diameter has light weight, easily flows along the flow,and is less likely to be affected by the inertia. Thus, such engine oiltends to be collected in a location where the stagnation or the likeoccurs. In view of this, wall surfaces that are connected at right angleare provided on an outer side of the route. In this way, it is possibleto further reliably separate the engine oil having the small particlediameter. The wall surfaces that are connected at right angle may beprovided not only to the reverse route 85 but also to another route.

The merging route 86 is a route in which the two branched routes by thebranching route 83 merge. In the merging route 86, the engine oilcollides with each other, which makes it easy to separate the engine oilfrom the blow-by gas. In particular, there is a case where the engineoil having the large particle diameter is integrated after the collisionwith each other, collides with the wall portion, and is consequentlyseparated from the blow-by gas. Thus, in the merging route 86, a wallportion preferably exists at a position where at least one of the twomerging routes is extended. The blow-by gas that has flowed through themerging route 86 flows into the above-mentioned fifth region 78, andthen flows into an intake system.

At least one of the first route 81 to the merging route 86 is alsoprovided in the regions other than the fourth region 77. Thus, in suchregions, it is possible to exert a similar effect to that describedabove and thus to separate the engine oil.

Next, a description will be made on a configuration of an oil deliveryportion 93 with reference to FIG. 5 and FIG. 6 . The oil deliveryportion 93 that is formed in the receiving plate 91 delivers the engineoil separated by the oil separation route. In this embodiment, since theoil return hole 92 and the introduction portion 71 are located at thesame position, it is necessary to deliver the engine oil in the reversedirection from the advancing direction of the blow-by gas in at least inpart. In FIG. 5 , a direction in which the oil delivery portion 93delivers the engine oil is indicated by bold arrows. In such portions,the oil delivery portion 93 is formed. The oil delivery portion 93 isconfigured to be able to guide the engine oil in a different directionfrom the flow direction of the blow-by gas.

More specifically, the oil delivery portion 93 is configured in a stepshape in which an up portion 93 a and a down portion 93 b arecontinuously and repeatedly provided. The up portion 93 a is a portion,a height of which is increased toward the downstream side of the routethrough which the engine oil returns. The down portion 93 b is aportion, a height of which is reduced toward the downstream side of theroute through which the engine oil returns. The height of the downportion 93 b is more steeply changed than that of the up portion 93 a.

Here, since the engine 100 vibrates, a delivery force of this vibrationcan move the engine oil on the slight gradient by the vibration. Thus,the engine oil can climb the up portion 93 a. Needless to say, theengine oil can also flow down the down portion 93 b. Furthermore, sincethe height of the down portion 93 b is steeply changed, the engine oilcannot climb the down portion 93 b by the vibration. Thus, the engineoil cannot move reversely in the down portion 93 b. As described so far,the engine oil moves along the flow direction thereof in the oildelivery portion 93. In particular, in this embodiment, the oil deliveryportion 93 is formed at a position that is recessed downward from thereceiving plate 91 (in other words, an upper end of the up portion 93 ais located on a lower side of the receiving plate 91). Accordingly, theengine oil is less likely to be affected by the blow-by gas that flowsreversely. Thus, it is possible to further reliably move the engine oil.Furthermore, the engine oil can be pooled in this groove-shaped portion.

As it has been described so far, the breather device 61 in thisembodiment separates the engine oil contained in the blow-by gas. Thisbreather device 61 includes the first route 81, the acceleration route82, the branching route 83, and the turn-back route 84. The blow-by gasflows through the first route 81. The acceleration route 82 is connectedto the downstream side of the first route 81 and has the smaller channelcross-sectional area than the first route 81. The branching route 83 isconnected to the downstream side of the acceleration route 82, includesthe wall portion that is orthogonal to the acceleration route 82, and isbranched into two routes by the wall portion. The turn-back route 84 isconnected to one of the branched routes of the branching route 83, andturns back in a manner to be parallel to the acceleration route 82 andobtain the reverse advancing direction from that of the accelerationroute 82.

In this way, the engine oil mist contained in the blow-by gas is carriedby the blow-by gas, the flow rate of which is increased in theacceleration route 82, and collides with the wall portion in thebranching route 83. As a result, the engine oil can be separated fromthe blow-by gas. In addition, since the turn-back route 84 causes theblow-by gas to turn back, the engine oil can be separated from theblow-by gas by inertia.

In regard to the breather device 61 of this embodiment, the breatherdevice 61 includes the portion (a corner portion) in which the advancingdirection of the route is changed by 90 degrees. The outer wall portions(a pair of the first wall portion 85 a and the second wall portion 85 band a pair of the second wall portion 85 b and the third wall portion 85c) constituting this corner portion are constructed of the two wallportions that are orthogonal to each other and are connected to eachother.

In this way, compared to the case where the wall portions constitutingthe outer side of the corner portion are connected by the arcuatesurface, the flow of the blow-by gas is likely to be disturbed andstagnate, and the flow rate of the blow-by gas is likely to be reduced.In particular, the engine oil mist having the small particle diameter islikely to be collected in the location, where the stagnation occurs, onthe outer side of the corner portion. As a result, it is possible tofurther reliably separate the engine oil from the blow-by gas.

The breather device 61 of this embodiment includes the merging routethat is formed on the downstream side of the branching route 83 and thatmerges the two branched routes of the branching route 83.

As a result, the engine oil that is contained in the two branched routescan collide with each other. Thus, it is possible to further reliablyseparate the engine oil from the blow-by gas.

The breather device 61 of this embodiment includes the receiving portion61 b that receives the engine oil separated from the blow-by gas. Thereceiving portion 61 b includes the oil delivery portion 93 thatdelivers the engine oil separated from the blow-by gas. The oil deliveryportion 93 is the stepped groove portion in which the up portion 93 aand the down portion 93 b are alternately and repeatedly provided. Theheight of the up portion 93 a is increased toward the downstream side ofthe route through which the engine oil returns. The height of the downportion 93 b is reduced toward the downstream side of the route throughwhich the engine oil returns. The height of the down portion 93 b ischanged more steeply than that of the up portion 93 a.

In this way, the engine oil can move along the up portion 93 a by thevibration of the engine. Meanwhile, since the height of the down portion93 b is steeply changed, the engine oil is less likely to flowreversely. As a result, it is possible to further reliably move theengine oil.

The engine 100 of this embodiment includes the breather device 61 andthe vaporizer 33. The vaporizer 33 vaporizes the liquid fuel by usingthe heat of the coolant. When the coolant that has been subjected to theheat exchange with the vaporizer 33 flows through the breather device61, the breather device 61 is cooled.

As a result, it is possible to increase the viscosity of the engine oilby cooling the blow-by gas in the breather device 61 using the coolant,the temperature of which has been reduced by the heat exchange with thevaporizer 33. Thus, it is possible to further reliably separate theengine oil from the blow-by gas.

The preferred embodiment of the present invention has been described sofar. However, the above configuration can be modified as follows, forexample.

The oil separation route described in the above embodiment is anexample, and a different route may be formed.

The engine 100 may include a supercharger that suctions the air by usingan exhaust turbine and a compressor. In this case, the compressor isarranged between the air cleaner 12 and the throttle valve 13 in theintake route.

DESCRIPTION OF REFERENCE NUMERALS

-   -   61 Breather device    -   81 First route    -   82 Acceleration route    -   83 Branching route    -   84 Turn-back route    -   85 Reverse route    -   100 Engine

The invention claimed is:
 1. A breather device that separates engine oilcontained in blow-by gas, the breather device comprising: a first routethrough which the blow-by gas flows; an acceleration route that isconnected to a downstream side of the first route and has a smallerchannel cross-sectional area than the first route; a branching routethat is connected to a downstream side of the acceleration route,includes a wall portion that is orthogonal to the acceleration route,and is branched into two routes by the wall portion; and a turn-backroute that is connected to one of the branched routes of the branchingroute and is turned back in a manner to be parallel to the accelerationroute and to have a reverse advancing direction from that of theacceleration route.
 2. The breather device according to claim 1 furthercomprising: a portion in which an advancing direction of the route ischanged by 90 degrees, wherein outer wall portions constituting theportion are constructed of two wall portions that are orthogonal to eachother and are connected to each other.
 3. The breather device accordingto claim 1 further comprising: a merging route that is formed on adownstream side of the branching route and that merges the two branchedroutes of the branching route.
 4. The breather device according to claim1, further comprising: a receiving portion that receives the engine oilseparated from the blow-by gas, wherein the receiving portion includesan oil delivery portion that delivers the engine oil separated from theblow-by gas, the oil delivery portion is a stepped groove portion inwhich an up portion and a down portion are alternately and repeatedlyprovided, a height of the up portion being increased toward a downstreamside of a route through which the engine oil returns, and a height ofthe down portion being reduced toward the downstream side of the routethrough which the engine oil returns, and the height of the down portionis changed more steeply than that of the up portion.
 5. An enginecomprising: the breather device according to claim 1; and a vaporizerthat vaporizes liquid fuel by using heat of an engine coolant, whereinthe breather device is cooled when the engine coolant that has beensubjected to heat exchange with the vaporizer flows through the breatherdevice.